The purpose of this research is to define in molecular terms, the nature of envelope gene recombination within the murine retroviruses. To this end, we are determining the amino acid sequences of the endogenous parental and recombinant virus gp70's of AKR mice. Using monoclonal antibodies directed specifically against the AKR 247 recombinant virus gp70, we are performing immunoaffinity chromatography to isolate 247 gp 70 and subsequent cleavage fragments for amino acid sequence analysis. We have defined the recombinant-specific regions of 247 gp70 and are now in the process of sequencing to determine the nature of the alterations brought about by recombination.